1. Field of the Invention
The present invention relates to combustion diagnostics.
2. Description of Related Art
In numerous industrial environments, a hydrocarbon fuel is burned in stationary combustors (e.g., boilers or furnaces) to produce heat to raise the temperature of a fluid, e.g., water. The fluid may be heated to generate steam, and this steam may be used to drive turbine generators that output electrical power. Such industrial combustors typically employ an array of many individual burner elements to combust the fuel. In addition, various means of combustion control, such as overfire air, staging air, reburning systems, selective non-catalytic reduction systems, can be employed in the post-flame zone of the burner elements to enhance combustion conditions and reduce nitrous oxide (NOx) emission.
For a combustor to operate efficiently and to produce an acceptably complete combustion that generates byproducts falling within the limits imposed by environmental regulations and design constraints, all individual burners in the combustor must operate cleanly and efficiently and all post-combustion systems must be properly balanced and adjusted. Emissions of unburned carbon (i.e., loss-on-ignition (LOI) data), NOx, carbon monoxide and/or other byproducts generally are monitored to ensure compliance with environmental regulations. The monitoring heretofore has been done, by necessity, on the aggregate emissions from the combustor (i.e., the entire burner array, taken as a whole).
Some emissions, such as the concentration of unburned carbon in fly ash, are difficult to monitor on-line and continuously. In most cases, these emissions are measured on a periodic or occasional basis, by extracting a sample of ash and sending the sample to a laboratory for analysis. When a particular combustion byproduct is found to be produced at unacceptably high concentrations, the combustor must be adjusted to restore proper operations. Measurement of the aggregate emissions, or measurement of emissions on a periodic or occasional basis, however, do not provide an indication of what combustor parameters should be changed and/or which combustor zone should be adjusted.
Applicant has recognized that it would be advantageous to achieve continuous, on-line monitoring of important combustion variables and their distribution in different combustion zones. If this monitoring is provided, individual burners and the post-flame combustion controls may be adjusted to provide an optimum, or improved, ratio among the fuel and air flows and to establish a distribution of individual air flows and reburning fuel flows resulting in efficient operation and emissions that are at acceptably low levels.
Applicant""s experimental testing has demonstrated that the fluctuating component of burner flame radiation is highly sensitive to changes in combustion conditions and parameters of that fluctuating component can be correlated with combustion variables and can be utilized to monitor, adjust and optimize the individual burners. Existing systems monitor the radiation from burner flame scanners and use signal processing algorithms to calculate combustion parameters based upon the characteristics of the signals output from the flame scanners. Although these systems operate satisfactorily in most situations, Applicant has recognized that the chaotic nature of burner flames tends to cause the combustion parameters calculated by them to be sporadically inconsistent with actual flame conditions. These intermittent inconsistencies can cause a person or system monitoring the parameters to believe falsely that one or more combustion variables require adjusting.
Additionally, Applicant has recognized that existing systems that monitor burner flames do not produce data indicative of the operating conditions of post-flame combustion systems, such as overfire air, staging air and reburning systems. These post-flame systems simply do not affect the condition of burner flames in a manner that is detectable by existing flame scanners and associated flame analysis systems. Existing flame analysis systems therefore are incapable of accurately monitoring the operation of such post-flame combustion systems and providing information regarding the failure or non-optimal operation thereof.
Also, Applicant has recognized that certain important combustion variables, such as the concentration of unburned carbon in fly ash, are difficult or even impossible to determine from flame scanners looking into the burner ignition zone because these parameters are formed outside of the ignition zone. Existing flame analysis systems therefore are incapable of accurately measuring such post-flame combustion variables.
Further, existing systems may employ frequency-domain analysis of flame scanner output signals. Such systems require instrumentation to transform time-domain signals into the frequency-domain. This instrumentation can be complicated and expensive. While these systems are capable of achieving accurate results, situations can be envisioned in which a lower cost system not requiring time-to-frequency-domain transformation instrumentation would be useful.
Sensors used to monitor flame conditions are susceptible to damage by combustibles or hot gases that come into contact with them. Sensors generally are placed in locations at which they are least likely to be damaged by these elements, and usually require continuous protection, e.g. by supplying purging or cooling air. The conventional manner in which scanners are mounted to monitor flame conditions leaves the scanners vulnerable to attack by potentially damaging flame-related forces and combustion products. In conventional systems, it is therefore difficult to maintain sensors in proper working condition, and frequent maintenance is required to be performed.
What is needed, therefore, is an improved system, apparatus and method for evaluating one or more combustion variables.
According to one aspect of the present invention, a method for analyzing operation of a combustor includes the steps of: (a) monitoring radiation emitted from a post-flame zone of the combustor, and (b) in response to a fluctuational component of the monitored radiation, calculating one or more combustion parameters.
According to another aspect of the invention, a method for analyzing operation of a combustor includes the steps of: (a) monitoring radiation emitted from the post-flame zone of the combustor; (b) generating a function that includes at least two extremum points, the function having a shape that changes in response to changes in a fluctuational component of the monitored radiation; and (c) using at least one coordinate of each of the at least two extremum points to calculate one or more combustion parameters.
According to another aspect, a method for analyzing operation of a combustor includes the steps of: (a) monitoring radiation emitted from the post-flame zone of the combustor; (b) analyzing a fluctuational component of the monitored radiation according to a first algorithm; (c) analyzing the fluctuational component of the monitored radiation according to a second algorithm; and (d) combining results of the first and second algorithms to calculate one or more combustion parameters.
According to yet another aspect, a method for analyzing operation of a combustor includes the steps of: (a) monitoring radiation emitted within the combustor; (b) producing a time-domain signal representing a measured amplitude of the monitored radiation; (c) calculating an average amplitude of the signal during a particular time period; (d) counting the number of high peaks in the signal that, during the particular time period, achieve an amplitude, relative to the average amplitude, that is greater than a first threshold, and/or a number of low peaks in the signal that, during the particular time period, achieve an amplitude, relative to the average amplitude, that is less than a second threshold; and (e) using the number of high peaks and/or the number of low peaks counted in step (d) to calculate one or more combustion parameters.
According to another aspect of the invention, a method for monitoring an amount of unburned carbon in fly ash includes the step of using an output of a radiation sensor monitoring radiation emitted from a post-flame zone of a combustor to monitor the amount of unburned carbon in fly ash.
According to yet another aspect, a method for analyzing operation of a combustor includes the steps of: (a) using a first radiation sensor, that is sensitive to a first portion of an electromagnetic spectrum, to monitor radiation emitted from the post-flame zone of the combustor; (b) using a second radiation sensor, that is sensitive to a second portion of the electromagnetic spectrum which is different from the first portion, to monitor radiation emitted from the post-flame zone of the combustor; and (c) in response to outputs of each of the first and second radiation sensors, calculating one or more combustion parameters.
According to another aspect of the present invention, a system for analyzing operation of a combustor includes: at least one radiation sensor arranged to monitor radiation emitted from a post-flame zone of the combustor and to produce a signal indicative thereof; and means for calculating at least one combustion parameter in response to a fluctuational component of the signal.
According to another aspect of the invention, a system for analyzing operation of a combustor includes: at least one radiation sensor to monitor radiation emitted from a post-flame zone of the combustor and to produce a signal indicative thereof; means for generating a function that includes at least two extremum points having a shape that changes in response to changes in the fluctuational component of the signal; and means for using at least one coordinate of each of the at least two extremum points calculate at least one combustion parameter.
According to another aspect, a system for analyzing operation of a combustor includes: at least one radiation sensor to monitor radiation emitted from a post-flame zone of the combustor and to produce a signal indicative thereof; means for analyzing a fluctuational component of the signal according to a first algorithm; means for analyzing the fluctuational component of the signal according to a second algorithm; and means for combining results of the first and second algorithms to calculate at least one combined combustion parameter.
According to yet another aspect of the invention, a system for analyzing operation of a combustor includes: at least one radiation sensor to monitor radiation emitted within the combustor and to produce a signal indicative thereof; means for calculating an average amplitude of the signal during a particular time period; and means for counting a number of high peaks in the signal that, during the particular time period, achieve an amplitude, relative to the average amplitude, that is greater than a first threshold, and/or a number of low peaks in the signal that, during the particular time period, achieve an amplitude, relative to the average amplitude, that is less than a second threshold; and means for using the number of high peaks and/or the number of low peaks counted by the means for counting to calculate at least one combustion parameter.
According to another aspect, a system for monitoring an amount of unburned carbon generated by a combustor includes: at least one radiation sensor to monitor radiation emitted from a post-flame zone of the combustor and to produce a signal indicative thereof; and means for using the signal to monitor the amount of unburned carbon generated by the combustor.
According to another aspect of the invention, a system for analyzing operation of a combustor includes: at least one first radiation sensor, that is sensitive to a first portion of an electromagnetic spectrum, to monitor radiation emitted from a post-flame zone of the combustor; at least one second radiation sensor, that is sensitive to a second portion of the electromagnetic spectrum which is different from the first portion, to monitor radiation emitted from a post-flame zone of the combustor; and means for calculating at least one combined combustion parameter in response to outputs of each of the first and second radiation sensors.
According to another aspect of the present invention, a computer-readable medium for use with a processor is disclosed. The medium has a plurality of instructions stored thereon which, when executed by the processor, cause the processor to perform the steps of: (a) in response to a fluctuational component of a signal generated by a radiation sensor the combustor, generating a function that includes at least two extremum points, the function having a shape that changes in response to changes in a fluctuational component of the signal; and (b) using at least one coordinate of each of the at least two extremum points to calculate at least one combustion parameter.
According to another aspect of the invention, a computer-readable medium for use with a processor is disclosed. The medium has a plurality of instructions stored thereon which, when executed by the processor, cause the processor to perform the steps of; (a) analyzing a fluctuational component of a signal generated by a radiation sensor monitoring radiation emitted from a post-flame zone of the combustor according to a first algorithm; (b) analyzing the fluctuational component of the signal according to a second algorithm; and (c) combining results of the first and second algorithms to calculate at least one combined combustion parameter.
According to another aspect, a computer-readable medium for use with a processor is disclosed. The medium has a plurality of instructions stored thereon which, when executed by the processor, cause the processor to perform the steps of: (a) calculating an average amplitude of a signal generated by a radiation sensor during a particular time period; (b) counting a number of high peaks in the signal that, during the particular time period, achieve an amplitude, relative to the average amplitude, that is greater than a first threshold, and/or a number of low peaks in the signal that, during the particular time period, achieve an amplitude, relative to the average amplitude, that is less than a second threshold; and (c) using the number of high peaks and/or the number of low peaks counted in step (b) to calculate at least one combustion parameter.
According to yet another aspect, a computer-readable medium for use with a processor is disclosed. The medium has a plurality of instructions stored thereon which, when executed by the processor, cause the processor to perform the step of using an output of a radiation sensor to monitor an amount of unburned carbon in fly ash.
According to another aspect of the present invention, a system for supporting a sensor near an outer surface of a combustor such that the sensor may sense combustion activity inside the combustor includes: a casing, forming a first channel through which gaseous matter may pass, and a member, forming a second channel, adapted to have a radiation sensor mounted thereto. When the apparatus is mounted on the combustor and the radiation sensor is mounted to the member, the second channel defines an unobstructed linear path that extends between the radiation sensor and a position inside the combustor, the unobstructed linear path intersecting at least a portion of the first channel.